In order to produce a cup from extruded foam plastic sheet, it is necessary to cut foamed sheet into either arcuate cup blanks and form the cup sidewalls in a manner known for paper cups and containers or to orient the extruded foam sheet, cut it into rectangular strips, form side-seamed cylinders from the strips and shrink the cylinders to the desired frusto-conical shapes.
Both methods result in the further necessity of heat or solvent sealing a bottom piece to the lowermost portion of the sidewalls.